Variable Valve Timing Actuator: Description and Operation

The valve timing unit turns the intake camshaft in relation to the primary chain to advance and retard the timing.

The unit consists of a body-and-sprocket assembly separated from an inner sleeve by a ring piston and two ring gears; the inner sleeve is bolted to the camshaft.

The ring gears engage in opposing helical splines on both body-and-sprocket assembly and inner sleeve to transmit drive from the assembly to the inner sleeve.

Engine-oil pressure moves the ring gears and piston to turn the inner sleeve in the advanced timing direction and a return spring reverses the direction for retard.

Additional springs absorb rotational and axial backlash to reduce noise and wear.